Thrust line vs center of mass

I’d be shocked if you didn’t defend Eurotubs, Abid. After all, you bought a set of manufacturing drawings and a license to build Eurotubs

But the bottom line is that all are Bensen derivatives as a result of using the Bensen rotor system.

Bensen combined Arthur Young’s underslung, teetering rotor with Cierva’s tilt head cyclic control system and added his version of the offset gimbal rotorhead, balanced against a trim spring.

Eurotubs using helicopter type cyclic control as does the A&S-18A would be much more difficult to fly and far more dangerous.
 
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I’d be shocked if you didn’t defend Eurotubs, Abid. After all, you bought a set of manufacturing drawings and a license to build Eurotubs

But the bottom line is that all are Bensen derivatives as a result of using the Bensen rotor system.

Bensen combined Arthur Young’s underslung, teetering rotor with Cierva’s tilt head cyclic control system and added his version of the offset gimbal rotorhead, balanced against a trim spring.

Eurotubs using helicopter type cyclic control as does the A&S-18A would be much more difficult to fly and far more dangerous.

Haha and I'd be surprised if you didn't dis them because they do not follow your prescription for achieving stability and instead rely on the HS for getting aoa stability. But that is not a meaningful statement. That is just a side play. I don't see Magni or others who make those types of machines come here and say things about "Erector Sets" or "Eiffel Towers".

I asked and have always asked if you have data that shows from the 6000+ units of the so called Eurotubs (they are more appropriately the design configuration that was finally set out by Juka who is an aeronautical engineer) have had significant number of PPOs in the last 25 years they have been flying?

Also, about why Raghu thought and showed the concepts and Physics of why these gyroplanes indeed are stable when he didn't have to care one way or the other then what is your counter to those concepts if any that make Raghu's work to be so easily set aside? Point by point. I know you know his work and have known it for years so lets just take his work in this reference.

And lastly, why do you think these machines are able to certify to BCAR Sec T which is quite stringent even on long period stability (when gyroplanes are not flying instrument flights).
 
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I got Raghu his first and only ride in a gyro; I asked Rusty Nance to give Raghu a ride in his 2-place Dominator.

Jean Fourcade is a far more credible source of advanced gyroplane theory.

But that’s all beside the point; the safety record of all gyros has improved over the years as a result of better training and improved design. And McCullough target drone engines have all been used up.

Eurotubs are not the handiwork of Jukka Tervamaki. Jukka interned at Bensen and the model he sold Magni was pretty much CLT. Magni tried to make his rendition of the prototype he purchased from Jukka look like a Ferrari. Also, Jukka produced some of the earliest FRP rotorblades, I think even beating MBB’s predecessor.
 
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I got Raghu his first and only ride in a gyro; I asked Rusty Nance to give Raghu a ride in his 2-place Dominator.

Jean Fourcade is a far more credible source of advanced gyroplane theory.

But that’s all beside the point; the safety record of all gyros has improved over the years as a result of better training and improved design. And McCullough target drone engines have all been used up.

Eurotubs are not the handiwork of Jukka Tervamaki. Jukka interned at Bensen and the model he sold Magni was pretty much CLT. Magni tried to make his rendition of the prototype he purchased from Jukka look like a Ferrari. Also, Jukka produced some of the earliest FRP rotorblades, I think even beating MBB’s predecessor.

Of course Raghu is not credible because he had few hours in a gyroplane. You know because to understand gyroplane stability you have to be an expert pilot not an engineer or a scientist. You know Chuck that is just not the case.

Jean Fourcade simply agrees with your view so he is a credible source of "advanced gyroplane theory".
Chuck, I asked what are your counters to Raghu's work point by point and safety regarding PPO on 6000 Eurotubs with HS?

I think this configuration is very much the work of Jukka. Of course Jukka interned with Bensen. So what. Everything is built on something and no Jukka is not obsessed with CLT or LTL. That is not his idea. If anything I can tell you from brief interaction with Jukka that he would very much be in Raghu's camp of why these gyroplanes are stable and why the data aligns with that theory.
 
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Abid, you claim to have studied math and physics at USF but as it turned out, you took a technician level course in micro electronics. Is it possible that someone read math and physics to you while you were looking at a semiconductor chip through a binocular microscope, trying to make a gold wire stick to a pad on the chip?

Whatever the case, Raghu did consulting work on the side and it seems likely that he was hired by MTO to write that report.

The only person I’m in complete agreement with is Juan de la Cierva. All of his gyroplanes were CLT with balance between belly fin and dorsal fin to eliminate throttle/yaw coupling and with differential pitch on the horizontal stabilizer to eliminate propeller/torque roll. Could he have been mistaken?
 
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the Bureau Enquète Accident said that the rotor was not providing lift any more

of course it means that the gyro was in a zero G situation, but the bea did not blame the engine torque even if it he mentioned in the report that the rotax computer showed that the engine was full throttle until the impact.
JM, government agencies do the best they can but they can’t be experts in everything.

A number of years ago, a friend of mine, Smokey, was at an airport with gyro when an FAA accident investigator arrived to investigate a fatal gyro accident. The investigator asked Smokey for assistance. Smokey said; “sure.”

They came to the wreckage and the investigator said: “Where’s the tail rotor?” Smokey said; “I don’t know.”

The investigator’s preliminary report blamed the accident on ‘loss of tail rotor.’
 
Section T approval has little credibility when concessions can be bought. It’s not the gold standard some would have us believe.

I prefer hands on experience over theory, I don’t have the ability to relate to cold facts and figures on a page – what speaks to me is the touch of three-dimensional reality in the sky. When decades of such experience are coupled with understanding of maths, physics etc, like Jean, Chuck and Doug, there’s no contest. Abid isn’t doing himself any favours. Agree to disagree and let it go.
 
Whatever the case, Raghu did consulting work on the side and it seems likely that he was hired by MTO to write that report.

CB, my friend what is this about? Why do you spread misinformation (or should I say fake news) ? What report are you talking about? Can you please correct your post? I have never consulted in any way or received any money from any gyro manufacturer. My interest is purely amateur and intellectual curiosity. My findings are what I best understand them to be-they could be correct or wrong. I am happy to discuss the work on its merits but don't have any interest in mud slinging.
 
CB, my friend what is this about? Why do you spread misinformation (or should I say fake news) ? What report are you talking about? Can you please correct your post? I have never consulted in any way or received any money from any gyro manufacturer. My interest is purely amateur and intellectual curiosity. My findings are what I best understand them to be-they could be correct or wrong. I am happy to discuss the work on its merits but don't have any interest in mud slinging.

Raghu
Good to see you are still here. I have not seen a post from you in years.
I thank you for truly getting deeper than high school Physics and providing an explanation that actually jives with reality and accident stats about PPO
 
Section T approval has little credibility when concessions can be bought. It’s not the gold standard some would have us believe.

I prefer hands on experience over theory, I don’t have the ability to relate to cold facts and figures on a page – what speaks to me is the touch of three-dimensional reality in the sky. When decades of such experience are coupled with understanding of maths, physics etc, like Jean, Chuck and Doug, there’s no contest. Abid isn’t doing himself any favours. Agree to disagree and let it go.

all certification standards even including Part 23 have provisions for exceptions but they do not apply to something as fundamental as longitudinal stability. Sec T longitudinal stability requirements are more stringent than Part 27 or CAR 4. The type certificates Gyroplanes in the US from the 60’s may not pass those requirements. Though that’s an educated guess only on my part.
 
jean-fourcade never agree with anyone except with maths and physics laws .... this man works for the european Nasa

the ctl is not an obsession but safety should be everyone's obsession

good for Jean. Then he can tell Chuck how to properly counter Raghu’s concepts and math and explain why every year from a fleet of thousands we don’t hear of dozens of PPO in Gyroplanes that are AoA stable. Easy. Stop appealing to authority and give clear explanation and counter real world data.
 
Abid, you claim to have studied math and physics at USF but as it turned out, you took a technician level course in micro electronics. Is it possible that someone read math and physics to you while you were looking at a semiconductor chip through a binocular microscope, trying to make a gold wire stick to a pad on the chip?

Whatever the case, Raghu did consulting work on the side and it seems likely that he was hired by MTO to write that report.

The only person I’m in complete agreement with is Juan de la Cierva. All of his gyroplanes were CLT with balance between belly fin and dorsal fin to eliminate throttle/yaw coupling and with differential pitch on the horizontal stabilizer to eliminate propeller/torque roll. Could he have been mistaken?
]

chuck before USF I already had dual major in engineering degrees. USF I did computer science.

I do not think your mud slinging merits a proper answer. If you don’t have data to counter stats or proper clear explanations for why Raghu’s work for instance isn’t valid, try and refrain from mud slinging. It doesn’t suit your age nor is it civil.
 
Be sure that I will read with attention Sir Raghu's scientific papers, let me know where they are published and I will with pleasure
If Mr Raghu issues a scientific paper showing that a gyroplane in Zero G at full power with a magni/mto/ela rudder can't flip up-side down on it's rolling axis I will carefully read this and if it convinces me I will be reassured... for the moment I am not reassured
As for the Authorities what do you fear as you claim that there is no problem ?
do you think that authorities could ban low profile gyros with magni/mto/ela style rudder only because I am speaking my mind on the internet ?
be reassured they haven't so far and there is little chance they will
99.9 % of the stock gyros are low profile gyros, so the competition of the High profile gyros doesn't even exists anymore so you are not commercially at risk at all Abid
I have my opinion based on the scientific papers I have read, you have yours based on other scientific papers and we are speaking on a forum where each reader will form his own opinion, if your point of View is the scientifically exact one, or if your force of conviction is the strongest, 99% of the readers will think you are right.
but you won't manage to prevent people to speak their mind.

you will have to go as far back as 2012 and go forward to 2015 to read all of Raghu’s posts on the subject to get the full context. When his work did not agree with this forum’s pre-eminent self claimed aerospace engineering Personality specializing in controls and stability, he got silently put aside.

Raghu has no dog in the fight but he had to put up with a lot. The problem is real world stats lean heavily in his favor. Theories have to explain reality not the other way around. Good luck searching, reading and understanding.
 
fara, this is another one I will have to remember " It doesn’t suit your age nor is it civil." Reminds me of one my boss said many years ago - a person can be unaware or unconcerned - translation ignorant and a dumbs__t.
 
I won't make any Archaeology in the forum, I am waiting for the same kind of paper then Jean fourcade's one, I am sure he can do this in order to reassure every body showing that a gyroplane in Zero G at full power with a magni/mto/ela rudder can't flip up-side down on it's rolling axis

Look at the summary
 
This is the most revealing PPO video that I've seen.


Of interest:

The craft has a H-stab but its volume is insufficient.

The pilot porpoises a little during his fast low pass.

The airspeed at the top of the zoom climb appears not to be great.

At the top of the zoom, the pilot pushes the stick forward, but soon yanks it back. The rotor follows the aft stick command but this has no effect on the developing pitchover.

Raghu's observation that a downdraft should not lead to a PPO in a gyro with an AOA-stable airframe is correct, with certain assumptions: (1) the H-stab is of sufficient volume (area x moment arm) and receives airflow unobstructed by other components (2) the rotor spindle stays at the same angle to the frame throughout the downdraft encounter (i.e the pilot does not "float" the stick, nor does he push it forward because he has gotten behind the aircraft), and (3) RRPM loss during the event is not great.

I like immersion of a downloaded H-stab in a HTL gyro because (if properly designed) it can more completely compensate for the pitching effect of the HTL when forward stick is applied. If the H-stab is not downloaded and/or is outside the propwash and airspeed is modest, then, when the stick is pushed forward, the nose of the craft will drop, amplifying the effect of the control input until the H-stab achieves enough of a negative AOA to arrest further nose-down rotation. Obviously, if the H-stab lacks sufficient potency, it will NEVER reach an AOA at which it arrests the PPO -- instead it will stall and the result may well be as seen on the video. A number of gyros WITH h-stabs have PPOed -- though AFAIK they've had either very small H-stabs (Bensens, etc.) or they have occuured in gyros with large engines, large HTL offsets and modest H-stab volume.

All of this talk concerns pitch stability only. Roll stability is another topic. Fortunately, roll stability can be achieved not only with immersed H-stabs, but just as well with immersed vertical fins, or immersed fins at angles between vertical and horizontal. Immersing fins for this purpose is especially handy, in that, if an anti-torque incidence is built into them, the counter-torque that they continuously apply to the frame will vary directly with throttle setting (or more precisely, with slipstream speed). The counter-torque of a non-immersed fin will vary with aircraft airspeed -- not always a good proxy for throttle setting.
 
all certification standards even including Part 23 have provisions for exceptions but they do not apply to something as fundamental as longitudinal stability. Sec T longitudinal stability requirements are more stringent than Part 27 or CAR 4. The type certificates Gyroplanes in the US from the 60’s may not pass those requirements. Though that’s an educated guess only on my part.
My guess is they would pass. Calculations I did years ago suggested that the J-2 and 18A are both CLT, plus they have generous horizontal stabilizers well back, plus articulated rotors that are relatively insensitive to low-g compared to the Bensen derivative style teetering systems. I recall no reports of any PIO or PPO in them. In flight, they are as pitch stable as any Cessna.
 
My guess is they would pass. Calculations I did years ago suggested that the J-2 and 18A are both CLT, plus they have generous horizontal stabilizers well back, plus articulated rotors that are relatively insensitive to low-g compared to the Bensen derivative style teetering systems. I recall no reports of any PIO or PPO in them. In flight, they are as pitch stable as any Cessna.

I was thinking of the long term stability requirement but you are likely right. I didn't think of the articulated rotor system
 
This is the most revealing PPO video that I've seen.


Of interest:

The craft has a H-stab but its volume is insufficient.

The pilot porpoises a little during his fast low pass.

The airspeed at the top of the zoom climb appears not to be great.

At the top of the zoom, the pilot pushes the stick forward, but soon yanks it back. The rotor follows the aft stick command but this has no effect on the developing pitchover.

...


There is a little plate for HS. Yeah that won't work.
 
There is a little plate for HS. Yeah that won't work.
When the forward speed is almost zero at the top of the trajectory, how large a not too little plate?
 
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